Description :

It is generally accepted that there is a link between the meteorological conditions and the occurrence of high ozone episodes during summer in the boundary layer. The current proposal combines the experience at RMI in the field of Numerical Weather Prediction with the experience in the field of ozone observations. This will be done by coupling the Chemical Transport Model CHIMÈRE with the analysed meteorological fields of ECMWF and ALADIN-Belgium runs. By the assimilation of ozone observations into the system, improved analysed fields of tropospheric ozone can be created. Not only the ground level observations of ozone, but also high-quality vertical ozone profiles from ozone soundings at Uccle will be used in the assimilation. The implementation of an assimilation scheme depends strongly on the treatment of the errors. Since there is already a long tradition of ozone observations this information is available.
The results of the assimilations will be used to extend our knowledge of the mechanisms leading to high ozone episodes, including vertical transport aspects. The improved analysed ozone fields can also be used to force the initial conditions of operational air quality forecast models.